A flat panel type display apparatus such as a liquid crystal display apparatus has currently been incorporated in various electronic devices due to the features of thinness, light weight, and low power consumption, and further due to the technical development for the enhancement of display performance such as coloring, increase in definition, and support for moving images. Examples of the electronic device having such a flat panel type display apparatus include a wide range of information devices, TV devices, and amusement devices, such as a mobile telephone, a PDA, a DVD player, a mobile game device, a notebook PC, a PC monitor, and a TV.
In such a background, for the purpose of further enhancing visibility and reducing power consumption in a display apparatus, a display system has been proposed, which has an automatic light control function of automatically controlling the brightness of the display apparatus in accordance with the use environment, in particular, the lightness of ambient light.
For example, JP 4(1992)-174819 A and JP 5(1993)-241512 A disclose a method for providing an optical sensor that is a discrete component in the vicinity of a display apparatus, and automatically controlling the brightness of the display apparatus based on the use environment illuminance detected by the optical sensor. Consequently, the display brightness is increased in a light environment such as the daytime or the outdoor, and the display brightness is decreased in a relatively dark environment such as the nighttime and the indoor. Thus, the adjustment of a brightness (light control) can be performed automatically in accordance with the lightness of an ambient environment. In this case, a viewer of the display apparatus does not feel screen glare in a dark environment, whereby the visibility can be enhanced. Furthermore, irrespective of the lightness/darkness of a use environment, the reduction in power consumption and the increase in life of a display apparatus can be achieved, compared with a use method for keeping a display brightness to be high at all times. Furthermore, the adjustment of a brightness (light control) is performed automatically based on the detection information of an optical sensor, so that a user is not bothered.
As described above, the display system having an automatic light control function can satisfy both the satisfactory visibility and the reduction in power consumption with respect to the change in lightness of a use environment. Therefore, such a display system is particularly useful for mobile devices (a mobile telephone, a PDA, a mobile game device, etc.) which are likely to be used outdoors and require the driving of a battery.
On the other hand, JP 2002-42856 A discloses a configuration in which an optical sensor that is a discrete component is incorporated in a display apparatus. FIG. 10 is an entire configuration view of a liquid crystal display apparatus disclosed by JP 2002-62856 A, and FIG. 11 is a cross-sectional view of an optical sensor mounting portion thereof. The liquid crystal display apparatus has a configuration in which a substrate (active matrix substrate) 901 on which active elements such as thin film transistors (TFTs) are formed and a counter substrate 902 are attached to each other, and a liquid crystal layer 903 is interposed in a region surrounded by a frame-shaped sealing member 925 in a gap between the substrates. In a peripheral portion of the active matrix substrate 901, i.e., in a peripheral region S (frame region) where the counter substrate is not present, optical sensors 907 that are discrete components are provided. Light is incident upon the optical sensors 907 through openings 916 provided in a housing 915.
Thus, the configuration in which the optical sensors 907 are provided in the above peripheral region S has the following features. More specifically, in the case where a display mode of a liquid crystal display apparatus is a transmission type or a semi-transmission type, it is necessary to provide a backlight system 914 on a reverse surface of the active matrix substrate 901; however, the optical sensors 907 are provided in the above peripheral region S, so that light emitted by the backlight system 914 does not reach the optical sensors 907 directly, whereby a malfunction of the optical sensors 907 caused by the light emitted by the backlight system 914 can be minimized. Furthermore, in a normal liquid crystal display apparatus, a polarizing plate (not shown) is attached to a front side of the counter substrate 902; however, the optical sensors 907 are provided in the above peripheral region S, so that ambient light incident upon the optical sensors 907 is not blocked by the polarizing plate on the counter substrate 902, whereby a sufficient amount of ambient light can be introduced into the optical sensors. Consequently, the optical sensors 907 can obtain a high S/N.
Furthermore, recently, the technique of producing a display apparatus has advanced rapidly, and a technique of forming IC chips and various circuit elements, which are conventionally mounted in a peripheral portion of a display apparatus as discrete components, in a display apparatus (specifically on a glass substrate constituting the display apparatus) monolithically by the same process during formation of circuits and elements constituting the display apparatus has been established.
For example, JP 2002-175026 A discloses an example in which a vertical driving circuit, a horizontal driving circuit, a voltage conversion circuit, a timing generation circuit, an optical sensor circuit, and the like are formed in a peripheral region of a display region monolithically by the same process, when the display region is formed on a substrate. The monolithic formation of such discrete components in the display apparatus enables the reduction in a component count and a component mounting process, and can realize the miniaturization and reduction in cost of an electronic device incorporating the display apparatus. Needless to say, an optical sensor used for the adjustment of a brightness (light control) of a display apparatus, a circuit dedicated for an optical sensor (light amount detection circuit), and the like can also be formed monolithically in a display apparatus. JP 2002-62856 A also discloses an embodiment in which a peripheral circuit and an optical sensor are formed on a substrate constituting a display apparatus monolithically by the same process, in place of an optical sensor that is a discrete component.
As an active element used in an active matrix type display apparatus, a thin film transistor (TFT) using an amorphous Si film or a polycrystalline Si film is generally used. In the case of forming active elements and various circuit elements monolithically on the same substrate as described above, a TFT using a polycrystalline Si film is mainly used.
Referring to FIG. 12, the configuration of a TFT having a polycrystalline Si film as a semiconductor layer, formed on each pixel of a pixel array region (display region) will be described. The configuration of a TFT described herein is called a “top gate structure” or a “forward stagger structure”, and has a gate electrode in an upper layer of a semiconductor film (polycrystalline Si film) to be a channel.
A TFT 500 includes a polycrystalline Si film 511 formed on a glass substrate 510, a gate insulation film 512 formed so as to cover the polycrystalline Si film, a gate electrode 513 formed on the gate insulation film 512, and a first interlayer insulation film 514 formed so as to cover the gate electrode 513. A source electrode 517 formed on the first interlayer insulation film 514 is electrically connected to a source region 511c of a semiconductor film via a contact hole passing through the first interlayer insulation film 514 and the gate insulation film 512. Similarly, a drain electrode 515 formed on the first interlayer insulation film 514 is electrically connected to a drain region 511b of a semiconductor film via a contact hole passing through the first interlayer insulation film 514 and the gate insulation film 512. Furthermore, a second interlayer insulation film 518 is formed so as to cover them.
In such a configuration, a region of the semiconductor film overlapping the gate electrode functions as a channel region 511a. Furthermore, regions of the semiconductor film other than the channel region 511a are doped with impurities in a high concentration, and function as the source region 511c and the drain region 511b. 
Although not shown, in order to prevent the degradation in electric characteristics caused by hot carriers, a lightly doped drain (LDD) region doped with impurities in a low concentration is formed on a channel region side of the source region 511c and on a channel region side of the drain region 511b. 
Furthermore, a pixel electrode 519 for supplying an electric signal to a display medium to be driven is formed in an upper layer of the second interlayer insulation film 518. The pixel electrode 519 is electrically connected to the drain electrode 515 via a contact hole provided in the second interlayer insulation film 518. The pixel electrode 519 is generally required to be flat in most cases, and the second interlayer insulation film 518 present in a lower layer of the pixel electrode 591 is required to have a function as a flattening film. Therefore, it is preferred that an organic film (thickness: 2 to 3 μm) made of acrylic resin is used for the second interlayer insulation film. Furthermore, for the purpose of forming a contact hole in the TFT 500 and taking out an electrode in a peripheral region, the second interlayer insulation film 518 is required to have patterning performance, and generally, an organic film having photosensitivity is used in most cases.
On the other hand, in the case where an optical sensor for detecting the lightness of ambient light is formed monolithically in a peripheral region of a display apparatus with a TFT-having the above configuration in a display region, if an attempt is made so as to minimize the increase in a production process, the element configuration of the optical sensor is limited.
FIG. 13 is a view showing an element configuration cross-section of an optical sensor 400 satisfying these conditions. A semiconductor film 411 constituting the optical sensor is formed on a glass substrate 410, and a doped region (a p-region 411c or an n-region 411b) of the semiconductor film 411 is formed in a lateral direction (plane direction) instead of a vertical direction (stack direction) with respect to a non-doped region (an i-region 411a). Generally, a configuration having a PIN junction in the lateral direction (plane direction) with respect to a formation surface is called a PIN-type photodiode with a lateral structure.
Each member constituting the optical sensor 400 is formed by the same process as that of each member constituting the TFT shown in FIG. 12. For example, an insulation film 412 formed of the same material and by the same process as those of the gate insulation film 512 is formed in an upper layer of the semiconductor film 411, and a p-side electrode 417 formed of the same material and by the same process as those of the source electrode 517 and an n-side electrode 415 formed of the same material and by the same process as those of the drain electrode 515 are formed in an upper layer of the first interlayer insulation film 414.
The optical sensor 400 shown in FIG. 13 can be used in place of the optical sensor 907 (a discrete component provided in a peripheral region) of a conventional display apparatus shown in FIG. 10, and can reduce a component count and a component mounting process, when the display apparatus shown in FIG. 10 is incorporated in an electronic device.
However, it was clarified that if an attempt is made so as to realize a display apparatus by forming the above-mentioned optical sensor shown in FIG. 13 in a peripheral region of an active matrix substrate, the following problems occur.
An active matrix substrate constituting a display apparatus is roughly divided into a display region (H shown in FIG. 11) and a peripheral region (frame region) (S shown in FIG. 11), and the latter peripheral region (S) can be further divided into a light shielding region (S1) shielded against light by the housing, and a non-light shielding region (S2) that is positioned in an opening (for example, corresponding to the opening 916 in FIG. 11) provided in the housing and receiving incidence of ambient light. The above-mentioned optical sensor needs to receive ambient light, so that the optical sensor needs to be placed in the non-light shielding region (S2) on the active matrix substrate.
With the above configuration, light with an entire wavelength contained in ambient light (solar light) is incident upon an optical sensor through the non-light shielding region (S2). A photodiode using the above-mentioned silicon thin film semiconductor is used preferably as an optical sensor. Such a photodiode has characteristics in which the sensitivity with respect to light in a short-wavelength region, i.e., UV-light increases relatively when the light with the entire wavelength is incident. Therefore, in spite of the fact that the adjustment of a brightness of a display apparatus originally needs to be performed in accordance with the lightness of visible light, there arises a problem that the optical sensor reacts with the intensity of UV-light, which makes it impossible to adjust a brightness appropriately.
In view of the above problems, an aspect of an example embodiment presented herein is to provide an electronic device that detects the lightness of visible light with high precision by preventing UV-light from being incident upon an optical sensor, and for example, can appropriately adjust the brightness of a display apparatus.
In order to solve the above problems, an electronic device according to the present embodiment including an active matrix substrate having a pixel array region in which a plurality of pixels are arranged and a display medium provided on the active matrix substrate, includes: an optical sensor provided in a peripheral region present in a periphery of the pixel array region in the active matrix substrate of the display apparatus; and a UV-light blocking member that is provided in a portion covering the optical sensor, and that transmits visible light and absorbs UV-light.
According to the above configuration, the UV-light blocking member is provided in a portion covering the optical sensor, whereby UV-light contained in ambient light can be prevented from reaching the optical sensor. Thus, the influence of UV-light on the detection precision of the optical sensor can be suppressed, and the lightness of visible light can be detected with high precision. Consequently, the brightness of the display apparatus can be adjusted appropriately so as to be matched with the visual characteristics of a human, for example, in accordance with the output results of the optical sensor.
In the electronic device according to the present embodiment, it is preferred that the UV-light blocking member attenuates a transmittance of UV-light contained in ambient light to 50% or less. This is because the adverse influence on the detection precision of the optical sensor caused by UV-light can be suppressed effectively.
In the electronic device according to the present embodiment, it is preferred that the UV-light blocking member is an acrylic plate.
It is preferred that the electronic device according to the present embodiment further includes a touch panel stacked on the display apparatus, and the touch panel includes the UV-light blocking member. This is because the constituent element of the touch panel also functions as the UV-light blocking member, whereby the influence of UV-light on the detection precision of the optical sensor can be suppressed without increasing a component count.
In the electronic device according to the present embodiment, it is preferred that at least a part of a constituent member of the optical sensor is produced by the same process as that of a constituent member of the active element. This is because a production process is simplified, which reduces a cost.
In the electronic device according to the present embodiment, it is preferred that the optical sensor is formed on a principal plane of the active matrix substrate monolithically. Herein, the optical sensor being “formed monolithically” on the active matrix substrate does not include the optical sensor being mounted on the active matrix substrate as a discrete component. More specifically, the optical sensor being “formed monolithically” on the active matrix substrate means that the optical sensor is formed on a principal plane of the active matrix substrate through the step in which the active matrix substrate is directly subjected to a physical and/or chemical process such as film formation treatment and etching treatment.
In the electronic device according to the present embodiment, it is preferred that in the pixel array region of the active matrix substrate, a plurality of electrode wires, a plurality of active elements, an interlayer insulation film provided in an upper layer of the plurality of electrode wires and the plurality of active elements, and a plurality of pixel electrodes formed on the interlayer insulation film are provided, and a transparent insulation layer made of the same material as that of the interlayer insulation film in the pixel array region is provided in an upper layer of the optical sensor. This is because the transparent insulation layer protects the optical sensor and the electrodes from outside air.
In the above electronic device, it is preferred that the interlayer insulation film and the transparent insulation layer are formed by the same process. This is because it is not necessary to increase the number of production steps, and the production cost of a display apparatus can be suppressed.
Furthermore, it is preferred that the electronic device according to the present embodiment further includes a transparent conductive layer made of the same material as that of the pixel electrode in an upper layer of the transparent insulation layer, and the transparent conductive layer is insulated from the pixel electrode in the pixel array region and is connected to a fixed potential. This is because the transparent conductive layer functions as an electromagnetic shield of the optical sensor to enhance the resistance to an electromagnetic noise of the optical sensor and an S/N ratio, which enables sensing with higher precision to be performed and can prevent the malfunction of peripheral circuits.
In the above-mentioned electronic device, it is preferred that the pixel electrode and the transparent conductive layer are formed by the same process. This is because the production cost of the display apparatus can be suppressed without increasing the number of production steps.
In the above-mentioned electronic device, for example, a thin film transistor can be used as the above-mentioned active element, and a photodiode having a lateral structure can be used as the environment sensor.
It is preferred that the electronic device according to the present embodiment further includes a control circuit that controls a display brightness in accordance with lightness information of ambient light detected by the optical sensor. The control of the display brightness can be realized when the control circuit controls the brightness of a backlight system, for example, in the case of the display apparatus with the backlight system. Furthermore, in the case where the display apparatus is a self-light emitting element, the control of the display brightness can be realized when the control circuit controls an emission brightness. Thus, by controlling the display brightness so as to obtain a necessary and sufficient brightness in accordance with the lightness of the circumstance, an electronic device that reduces power consumption and realizes an easy-to-see display can be provided. The electronic device can satisfy both the satisfactory visibility and the reduction in power consumption with respect to the change in lightness of a use environment, so that it is particularly useful as a mobile device which is likely to be used outdoors and requires the driving of a battery. Specific examples of such a mobile device are not limited to the application of the present invention, and include, for example, an information terminal such as a mobile telephone and a PDA, a mobile game device, a portable music player, a digital camera, and a video camera.
As described above, according to the present invention, an electric device can be provided, which detects the lightness of visible light with high precision by preventing UV-light from being incident upon an optical sensor, and for example, can appropriately adjust the brightness of a display apparatus.